Preventive pillar reinforcement methodology incorporating instrumentation and extraction strategy at the Chuquicamata underground mine

Authors: López Norambuena, S; Alegria, JP; Ossandon Pardo, M; Quiroz Alegría, R Download Paper Open access courtesy of:

DOI https://doi.org/10.36487/ACG_repo/2645_22

Cite As:
López Norambuena, S, Alegria, JP, Ossandon Pardo, M & Quiroz Alegría, R 2026, 'Preventive pillar reinforcement methodology incorporating instrumentation and extraction strategy at the Chuquicamata underground mine', in A van As, D Cumming-Potvin & J Wesseloo (eds), Caving 2026: Proceedings of the Sixth International Conference on Block and Sublevel Caving, Australian Centre for Geomechanics, Perth, pp. 1-16, https://doi.org/10.36487/ACG_repo/2645_22



Abstract:
The mining method used at the Chuquicamata underground mine is post-undercut block caving, in which, after the base of the block is undercut, the natural caving and fragmentation of the rock mass occurs. The behaviour of rock pillars at Chuquicamata underground evolves through 2 main stages. The first stage corresponds to the response to stresses induced by the advancing cave front (abutment stress), representing a pre-connection period during which production level pillars begin to deform and cracking develops. The second stage occurs after connection to the surface, when the pillars experience increased deformation due to deconfinement, directly affecting the installed ground support. This study focuses on the preventive definition of reinforcement measures for production pillars, with the objective of anticipating further increases in deformation and ensuring the stability of the productive areas. The analysis is based on seismic activity, where variations in apparent volume and energy index are evaluated to identify increasing deformation and a reduction in stress levels (loss of confinement). These responses are validated using pillar extensometer measurements, drift scanning and assessments of production excavations and local geotechnical conditions. Based on the evaluation of these responses, different reinforcement alternatives are jointly defined with the mine operational teams. These alternatives are required to be coordinated with the production plans of each productive area. This approach enables the development of a preventive pillar reinforcement plan, together with an extraction strategy aimed at controlling deformation increments across different zones, thereby ensuring the stability and continuity of the mine’s productive areas.

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